1. Field of the Invention
This invention relates to vacuum assisted molding. More particularly, it relates to fabrication of hollow, seamless composite elements of any size using a low pressure vacuum infusion system supplemented by multiple cooperative centrifugal forces.
2. Description of the Prior Art
The manufacturing of large molded objects, such as boat hulls, large blades for an electricity-generating wind turbine, and the like, is problematic. Such large objects are typically molded by a time-consuming manual process. This drives up the cost of the individual products. Items made by manual labor are also more likely to be of inconsistent quality as no two products will be exactly alike.
Injection molding systems for large objects require pressures, typically, of about three thousand pounds per square inch (3,000 lbs/in2). This requires very large and strong holding devices to hold the mold halves closed. Moreover, a seam is formed where the mold halves meet. A part made in such conventional fashion may fail at the seams. For example, large blades rotated by wind for electricity generation often fail by coming apart at the seams. Such catastrophic failures can fling large heavy parts across long distances, causing damage to people, animals, and property.
What is needed, then, is a new, low pressure manufacturing process for making molded but seamless monolithic products of any size and shape. More particularly, there is a need for a manufacturing process that reduces the amount of manual labor needed to produce such objects and that reduces the pressures down to about fifteen pounds per square inch (15 lbs/in2) thereby eliminating the large holding devices of injection molded systems. The needed process would substantially reduce the cost of such molded objects. There is also a need for a new process that produces both large and small molded products having consistently high quality.
However, in view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in this art how the identified needs could be met.